NON-POLAR (Al,B,In,Ga)N QUANTUM WELLS

ABSTRACT

A method of fabricating non-polar a-plane GaN/(Al,B,In,Ga)N multiple quantum wells (MQWs). The a-plane MQWs are grown on the appropriate GaN/sapphire template layers via metalorganic chemical vapor deposition (MOCVD) with well widths ranging from 20 Å to 70 Å. The room temperature photoluminescence (PL) emission energy from the a-plane MQWs followed a square well trend modeled using self-consistent Poisson-Schrodinger (SCPS) calculations. Optimal PL emission intensity is obtained at a quantum well width of 52 Å for the a-plane MQWs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of the following co-pending andcommonly-assigned Patent Application:

U.S. Utility patent application No. 10/582,390, filed Jun. 9, 2006, byMichael D. Craven and Steven P. DenBaars, entitled “NON-POLAR(Al,B,In,Ga)N QUANTUM WELLS,” attorneys docket number 30794.104-US-WO,which application claims priority to International Patent ApplicationNo. PCT/US03/39355, filed Dec. 11, 2003, by Michael D. Craven and StevenP. DenBaars, entitled “NON-POLAR (Al,B,In,Ga)N QUANTUM WELLS,” attorneysdocket number 30794.104-WO-01, which application is acontinuation-in-part of the following co-pending and commonly-assignedPatent Applications:

International Patent Application No. PCT/US03/21918, filed Jul. 15,2003, by Benjamin A. Haskell, Michael D. Craven, Paul T. Fini, Steven P.DenBaars, James S. Speck, and Shuji Nakamura, entitled “GROWTH OFREDUCED DISLOCATION DENSITY NON-POLAR GALLIUM NITRIDE BY HYDRIDE VAPORPHASE EPITAXY,” attorneys docket number 30794.93-WO-U1, whichapplication claims priority to U.S. Provisional Patent Application Ser.No. 60/433,843, filed Dec. 16, 2002, by Benjamin A. Haskell, Michael D.Craven, Paul T. Fini, Steven P. DenBaars, James S. Speck, and ShujiNakamura, entitled “GROWTH OF REDUCED DISLOCATION DENSITY NON-POLARGALLIUM NITRIDE BY HYDRIDE VAPOR PHASE EPITAXY,” attorneys docket number30794.93-US-P1;

International Patent Application No. PCT/US03/21916, filed Jul. 15,2003, by Benjamin A. Haskell, Paul T. Fini, Shigemasa Matsuda, MichaelD. Craven, Steven P. DenBaars, James S. Speck, and Shuji Nakamura,entitled “GROWTH OF PLANAR, NON-POLAR A-PLANE GALLIUM NITRIDE BY HYDRIDEVAPOR PHASE EPITAXY,” attorneys docket number 30794.94-WO-U1, whichapplication claims priority to U.S. Provisional Patent Application Ser.No. 60/433,844, filed Dec. 16, 2002, by Benjamin A. Haskell, Paul T.Fini, Shigemasa Matsuda, Michael D. Craven, Steven P. DenBaars, James S.Speck, and Shuji Nakamura, entitled “TECHNIQUE FOR THE GROWTH OF PLANAR,NON-POLAR A-PLANE GALLIUM NITRIDE BY HYDRIDE VAPOR PHASE EPITAXY,”attorneys docket number 30794.94-US-P1;

U.S. Utility patent application Ser. No. 10/413,691, filed Apr. 15,2003, by Michael D. Craven and James S. Speck, entitled “NON-POLARA-PLANE GALLIUM NITRIDE THIN FILMS GROWN BY METALORGANIC CHEMICAL VAPORDEPOSITION,” attorneys docket number 30794.100-US-U1, which applicationclaims priority to U.S. Provisional Patent Application Ser. No.60/372,909, filed Apr. 15, 2002, by Michael D. Craven, Stacia Keller,Steven P. DenBaars, Tal Margalith, James S. Speck, Shuji Nakamura, andUmesh K. Mishra, entitled “NON-POLAR GALLIUM NITRIDE BASED THIN FILMSAND HETEROSTRUCTURE MATERIALS,” attorneys docket number 30794.95-US-P1;

U.S. Utility patent application Ser. No. 10/413,690, filed Apr. 15,2003, by Michael D. Craven, Stacia Keller, Steven P. DenBaars, TalMargalith, James S. Speck, Shuji Nakamura, and Umesh K. Mishra, entitled“NON-POLAR (Al,B,In,Ga)N QUANTUM WELL AND HETEROSTRUCTURE MATERIALS ANDDEVICES, attorneys docket number 30794.101-US-U1, which applicationclaims priority to U.S. Provisional Patent Application Ser. No.60/372,909, filed Apr. 15, 2002, by Michael D. Craven, Stacia Keller,Steven P. DenBaars, Tal Margalith, James S. Speck, Shuji Nakamura, andUmesh K. Mishra, entitled “NON-POLAR GALLIUM NITRIDE BASED THIN FILMSAND HETEROSTRUCTURE MATERIALS,” attorneys docket number 30794.95-US-P1;

U.S. Utility patent application Ser. No. 10/413,913, filed Apr. 15,2003, by Michael D. Craven, Stacia Keller, Steven P. DenBaars, TalMargalith, James S. Speck, Shuji Nakamura, and Umesh K. Mishra, entitled“DISLOCATION REDUCTION IN NON-POLAR GALLIUM NITRIDE THIN FILMS,”attorneys docket number 30794.102-US-U1, which application claimspriority to U.S. Provisional Patent Application Ser. No. 60/372,909,filed Apr. 15, 2002, by Michael D. Craven, Stacia Keller, Steven P.DenBaars, Tal Margalith, James S. Speck, Shuji Nakamura, and Umesh K.Mishra, entitled “NON-POLAR GALLIUM NITRIDE BASED THIN FILMS ANDHETEROSTRUCTURE MATERIALS,” attorneys docket number 30794.95-US-P1;

all of which applications are incorporated by reference herein.

FIELD OF THE INVENTION

The invention is related to semiconductor materials, methods, anddevices, and more particularly, to non-polar (Al,B,In,Ga)N quantumwells.

DESCRIPTION OF THE RELATED ART

(Note: This application references a number of different publications asindicated throughout the specification by one or more reference numbers.A list of these different publications ordered according to thesereference numbers can be found below in the section entitled“References.” Each of these publications is incorporated by referenceherein.)

Currently, state-of-the-art nitride-based epitaxial device structuresare grown along the polar c-axis of the thermodynamically stablewurtzite (Al,Ga,In)N unit cell. Due to the strong polarization constantsof the nitrides [1], interfacial polarization discontinuities withinheterostructures are associated with fixed sheet charges which producestrong internal electric fields. These “built-in” polarization-inducedelectric fields limit the performance of optoelectronic devices whichemploy quantum well active regions. Specifically, the spatial separationof the electron and hole wavefunctions caused by the internal fields,i.e., the quantum confined Stark effect (QCSE), reduces the oscillatorstrength of transitions and ultimately restricts the recombinationefficiency of the quantum well [2]. Nitride crystal growth alongnon-polar directions provides an efficient means of producingnitride-based quantum structures that are unaffected by these strongpolarization-induced electric fields since the polar axis lies withinthe growth plane of the film.

(1 100) m-plane GaN/AlGaN multiple quantum well (MQW) structures werefirst demonstrated by plasma-assisted molecular beam epitaxy (MBE) usinglithium aluminate substrates [3]. Since this first demonstration,free-standing m-plane GaN substrates grown by hydride vapor phaseepitaxy (HVPE) were employed for subsequent epitaxial GaN/AlGaN MQWgrowths by both MBE [4] and metalorganic chemical vapor deposition(MOCVD) [5]. In addition to the m-plane, research efforts haveinvestigated a-plane GaN/AlGaN MQW structures grown on r-plane sapphiresubstrates by both MBE [6] and MOCVD [7]. Optical characterization ofthese structures has shown that non-polar quantum wells are unaffectedby polarization-induced electric fields.

The present invention describes the dependence of a-plane GaN/AlGaN MQWemission on the GaN quantum well width. Moreover, an investigation of arange of GaN well widths for MOCVD-grown a-plane and c-plane MQWsprovides an indication of the emission characteristics that are uniqueto non-polar orientations.

SUMMARY OF THE INVENTION

The present invention describes a method of fabricating non-polara-plane GaN/(Al,B,In,Ga)N multiple quantum wells (MQWs). In this regard,a-plane MQWs were grown on the appropriate GaN/sapphire template layersvia metalorganic chemical vapor deposition (MOCVD) with well widthsranging from 20 Å to 70 Å. The room temperature photoluminescence (PL)emission energy from the a-plane MQWs followed a square well trendmodeled using self-consistent Poisson-Schrodinger (SCPS) calculations.Optimal PL emission intensity is obtained at a quantum well width of 52Å for the a-plane MQWs.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIG. 1 is a flowchart that illustrates the steps of a method for formingnon-polar a-plane GaN/(Al,B,In,Ga)N quantum wells according to apreferred embodiment of the present invention.

FIG. 2 is a graph of high-resolution x-ray diffraction (HRXRD) scans ofsimultaneously regrown a-plane (69 Å GaN)/(96 Å Al_(0.16)Ga_(0.84)N) andc-plane (72 Å GaN)/(98 Å Al_(0.16)Ga_(0.84)N) MQW stacks. In addition tothe quantum well dimensions, the HRXRD profiles provide a qualitativecomparison of the MQW interface quality through the full width at halfmaximum (FWHM) of the satellite peaks.

FIGS. 3( a) and (b) are graphs of room temperature PL spectra of the (a)a-plane and (b) c-plane GaN/(100 Å Al_(0.16)Ga_(0.84)N) MQWs with wellwidths ranging from 20 Å-70 Å. The vertical gray line on each plotdenotes a band edge of the bulk GaN layers.

FIG. 4 is a graph of the well width dependence of the room temperaturePL emission energy of the a-plane and c-plane MQWs. The dotted line isthe result of self-consistent Poisson-Schrodinger (SCPS) calculationsfor a flat-band GaN/(100 Å Al_(0.16)Ga_(0.84)N) MQW. The emission energydecreases with increasing well width for both growth orientations butabove a critical well width, the c-plane MQW emission energy red-shiftsbelow the band edge of the GaN layers.

FIG. 5 is a graph of the normalized room temperature PL intensityplotted as a function of GaN quantum well width for both a-plane andc-plane growth orientations. The data for each orientation is normalizedseparately, hence direct comparisons between the relative intensities ofa-plane and c-plane MQWs are not possible.

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the preferred embodiment, reference ismade to the accompanying drawings which form a part hereof, and in whichis shown by way of illustration a specific embodiment in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

Overview

Non-polar nitride-based semiconductor crystals do not experience theeffects of polarization-induced electric fields that dominate thebehavior of polar nitride-based quantum structures. Since thepolarization axis of a wurtzite nitride unit cell is aligned parallel tothe growth direction of polar nitride crystals, internal electric fieldsare present in polar nitride heterostructures. These “built-in” fieldshave a detrimental effect on the performance of state-of-the-artoptoelectronic and electronic devices. By growing nitride crystals alongnon-polar directions, quantum structures not influenced bypolarization-induced electric fields are realized. Since the energy bandprofiles of a given quantum well change depending upon the growthorientation, different scientific principles must be applied in order todesign high performance non-polar quantum wells. This inventiondescribes the design principles used to produce optimized non-polarquantum wells.

Process Steps

FIG. 1 is a flowchart that illustrates the steps of a method for formingquantum wells according to a preferred embodiment of the presentinvention. The steps of this method grow non-polar a-plane GaN/AlGaNMQWs on a-plane GaN/r-plane sapphire template layers.

Block 100 represents loading of a sapphire substrate into a vertical,close-spaced, showerhead MOCVD reactor. For this step, epi-readysapphire substrates with surfaces crystallographically oriented within+/−2° of the sapphire r-plane may be obtained from commercial vendors.No ex-situ preparations need be performed prior to loading the sapphiresubstrate into the MOCVD reactor, although ex-situ cleaning of thesapphire substrate could be used as a precautionary measure.

Block 102 represents annealing the sapphire substrate in-situ at a hightemperature (>1000° C.), which improves the quality of the substratesurface on the atomic scale. After annealing, the substrate temperatureis reduced for the subsequent low temperature nucleation layerdeposition.

Block 104 represents depositing a thin, low temperature, low pressure,nitride-based nucleation layer as a buffer layer on the sapphiresubstrate. Such layers are commonly used in the heteroepitaxial growthof c-plane (0001) nitride semiconductors. In the preferred embodiment,the nucleation layer is comprised of, but is not limited to, 1-100nanometers (nm) of GaN deposited at approximately 400-900° C. and 1 atm.

After depositing the nucleation layer, the reactor temperature is raisedto a high temperature, and Block 106 represents one or more growingunintentionally doped (UID) a-plane GaN layers to a thickness ofapproximately 1.5 μm on the nucleation layer deposited on the substrate.The high temperature growth conditions include, but are not limited to,approximately 1100° C. growth temperature, 0.2 atm or less growthpressure, 30 μmol per minute Ga flow, and 40,000 μmol per minute N flow,thereby providing a V/III ratio of approximately 1300). In the preferredembodiment, the precursors used as the group III and V sources aretrimethylgallium, ammonia and disilane, although alternative precursorscould be used as well. In addition, growth conditions may be varied toproduce different growth rates, e.g., between 5 and 9 Å per second,without departing from the scope of the present invention.

Upon completion of the high temperature growth step, Block 108represents cooling the epitaxial a-plane GaN layers down under anitrogen overpressure.

Finally, Block 110 represents one or more (Al,B,In,Ga)N layers beinggrown on the a-plane GaN layers. Preferably, these grown layers comprise˜100 Å Al_(0.16)Ga_(0.84)N barriers doped with an Si concentration of˜2×10¹⁸ cm⁻³. Moreover, the above Blocks may be repeated as necessary.In one example, Block 110 was repeated 10 times to form UID GaN wellsranging in width from approximately 20 Å to approximately 70 Å.

Experimental Results

For non-polar nitride quantum wells, flat energy band profiles exist andthe QCSE is not present. Consequently, non-polar quantum well emissionis expected to follow different trends as compared to polar quantumwells. Primarily, non-polar quantum wells exhibit improved recombinationefficiency, and intense emission from thicker quantum wells is possible.Moreover, the quantum well width required for optimal non-polar quantumwell emission is larger than for polar quantum wells.

The following describes the room temperature PL characteristics ofnon-polar GaN/(18 100 Å Al_(0.16)Ga_(0.84)N) MQWs in comparison toc-plane structures as a function of quantum well width. To accomplishthis, 10-period a-plane and c-plane MQWs structures were simultaneouslyregrown on the appropriate GaN/sapphire template layers via MOCVD withwell widths ranging from approximately 20 Å to 70 Å.

Kinematic analysis of HRXRD measurements [9] made with a Philips MRDXPERT PRO™ diffractometer using CuK_(α1) radiation in triple axis modeconfirmed the quantum well dimensions and barrier composition. Roomtemperature continuous-wave (c-w) PL spectroscopy using the 325 nm lineof a He—Cd laser (excitation power density ˜10 W/cm2) was used tocharacterize the MQW emission properties.

FIG. 2 is a graph of HRXRD scans of simultaneously regrown a-plane 69 ÅGaN/96 Å Al_(0.16)Ga_(0.84)N and c-plane 72 Å GaN/98 ÅAl_(0.16)Ga_(0.84)N MQW stacks. In addition to the quantum welldimensions, the HRXRD profiles provide a qualitative comparison of theMQW interface quality through the FWHM of the satellite peaks.

The on-axis 2θ-ω scans of the a-plane and c-plane structures were takenabout the GaN (11 20) and (0004) reflections, respectively. Analysis ofthe x-ray profiles yields both the aluminum composition x of theAl_(x)Ga_(1-x)N barriers and the quantum well dimensions (well andbarrier thickness), which agree within 7% for the simultaneously growna-plane and c-plane samples indicating a mass transport limited MOCVDgrowth regime. Both HRXRD profiles reveal superlattice (SL) peaks out tothe second order in addition to strong reflections from the GaN layers.The FWHMs of the SL peaks provide a qualitative metric of the quantumwell interface quality [10]; therefore, from the scans shown in FIG. 2,a conclusion can be made that the interface quality of a-plane MQWs isinferior to that of the c-plane samples. Analysis of the a-plane MQWstructural quality (described in [9]) revealed sharp interfaces despitethe large threading dislocation density extending through the MQW fromthe a-GaN template. The higher threading dislocation (TD) density andincreased surface roughness of the a-plane growth in comparison toc-plane are the most likely causes for greater a-plane MQW interfaceroughness and SL peak broadening. Additionally, it is estimated that thea-plane TD density is approximately two orders of magnitude greater thanthe c-plane TD density.

FIGS. 3( a) and (b) are graphs of room temperature PL spectra of the (a)a-plane and (b) c-plane GaN/(100 Å Al_(0.16)Ga_(0.84)N) MQWs with wellwidths ranging from ˜20 Å to ˜70 Å. The vertical gray line on each plotdenotes the bulk GaN band edge.

Independent of crystal orientation, the MQW PL emission shifts to longerwavelengths (equivalently, the PL emission decreases) with increasingquantum well width as the quantum confinement is reduced.

In particular, the emission energies of the a-plane MQWs steadilyapproach but do not red-shift beyond the bulk GaN band edge as the wellwidth increases. The resistive nature of UID a-GaN films prevents bandedge emission at room temperature, resulting in emissions only from thequantum wells, as is observed in FIG. 3( a).

Conversely, the c-plane MQW emission energy red-shifts below the GaNband edge when the GaN quantum well width is increased from 38 Å to 50Å. For polar GaN wells wider than 50 Å, only PL emission from theunderlying GaN was detected. The appearance of c-GaN buffer emissionimplies that the c-plane template has a lower native point defectdensity than the a-plane template. Furthermore, yellow band emission wasobserved for both the non-polar and polar MQWs; therefore, the origin ofdeep trap levels is most likely the growth conditions required tomaintain the a-plane morphology and not a characteristic of thenon-polar orientation.

The two primary features of the PL emission spectra, the emission energyand the emission intensity, are summarized in FIGS. 4 and 5,respectively, as functions of quantum well width. The emission energydecreases with increasing well width due to quantum confinement effects.

FIG. 4 is a graph of the well width dependence of the room temperaturePL emission energy of the a-plane and c-plane MQWs. For all quantum wellwidths studied, the a-plane MQW emission is blue-shifted with respect tothe bulk GaN band edge and the blue-shift increases with decreasing wellwidth as quantum confinement raises the quantum well's ground-stateenergy. The a-plane MQW emission energy trend is modeled accuratelyusing square well SCPS calculations [11] shown as the dotted line inFIG. 4. The agreement between theory and experiment confirms thatemission from non-polar MQWs is not influenced by polarization-inducedelectric fields. Despite this agreement, the theoretical modelincreasingly over-estimates the experimental data with decreasingquantum well width by 15 to 35 meV. The deviating trend can be explainedby the expected increase in exciton binding energy with decreasing wellwidth for GaN/AlGaN MQWs [12,13], since exciton binding energies are notaccounted for in the SCPS model. Conversely, FIG. 4 shows the dramaticred-shift in c-plane MQW emission with increasing well width, a widelyobserved trend dictated by the QCSE [14-18]. Specifically, theexperimental c-plane MQW emission energy trend agrees with the model ofthe polar QW ground state proposed by Grandjean et al. [13].Interpolating the experimental data, the emission from c-plane MQWs withGaN well widths greater than ˜43 Å is below the bulk GaN band edge.Increasing the well thickness increases the spatial separation of chargecarriers within the quantum wells and the recombination efficiency isreduced until MQW emission is no longer observed (wells wider than 50Å). Previously reported emission from an a-plane (107 Å GaN)/(101 ÅAl_(0.25)Ga_(0.75)N) MQW [9] provides additional evidence of theimproved quantum efficiency for non-polar MQWs.

FIG. 5 is a graph of the normalized room temperature PL emissionintensity plotted as a function of GaN quantum well width for botha-plane and c-plane growth orientations. The data for each orientationis normalized separately, hence direct comparisons between the relativeintensities of a-plane MQWs and c-plane MQWs are not possible. Since themicrostructural quality of the template layers is substantiallydifferent, a direct comparison between a-and c-plane MQW emissionintensity would be inconclusive.

A maximum a-plane MQW emission intensity is associated with an optimalquantum well width of 52 Å, while the maximum c-plane emission intensityis observed for 28 Å-wide wells. As a result of the QCSE, optimalemission intensity is obtained from relatively thin polar GaN quantumwells (20 Å-35 Å) depending on the thickness and composition of theAlGaN barrier layers [13]. The balance between reduced recombinationefficiency in thick wells and the reduced recombination due to increasednonradiative transitions at heterointerfaces and extension of electronwavefunctions outside of thin wells [19] determines the optimal c-planewell width. Conversely, since the non-polar MQWs do not experience theQCSE, it is expected that the optimal well width is determined bymaterial quality, interface roughness, and the excitonic Bohr radius.Although the interface roughness of the a-plane structures is greaterthan the c-plane, the advantageous effects of a non-polar orientationare apparent. Also note that, with improved non-polar surface andinterface quality, the optimal well width will most likely shift fromthe optimal width observed for these samples.

REFERENCES

The following references are incorporated by reference herein:

1. F. Bernardini, V. Fiorentini, and D. Vanderbilt, Phys. Rev. B 56,R10024 (1997).

2. T. Takeuchi, H. Amano, and I. Akasaki, Jpn. J. Appl. Phys. 39, 413(2000).

3. P. Waltereit, O. Brandt, A. Trampert, H. T. Grahn, J. Menniger, M.Ramsteiner, M. Reiche, and K. H. Ploog, Nature 406, 865 (2000).

4. A. Bhattacharyya, I. Friel, S. Iyer, T. C. Chen, W. Li, J. Cabalu, Y.Fedyunin, K. F. Ludwig, T. D. Moustakas, H. P. Maruska, D. W. Hill, J.J. Gallagher, M. C. Chou, and B. Chai, J. Cryst. Growth 251, 487 (2003).

5. E. Kuokstis, C. Q. Chen, M. E. Gaevski, W. H. Sun, J. W. Yang, G.Simin, M. A. Khan, H. P. Maruska, D. W. Hill, M. C. Chou, J. J.Gallagher, and B. Chai, Appl. Phys. Lett. 81, 4130 (2002).

6. H. M. Ng, Appl. Phys. Lett. 80, 4369 (2002).

7. M. D. Craven, S. H. Lim, F. Wu, J. S. Speck, and S. P. DenBaars,Appl. Phys. Lett. 81, 469 (2002).

8. B. P. Keller, S. Keller, D. Kapolnek, W. N. Jiang, Y. F. Wu, H.Masui, X. Wu, B. Heying, J. S. Speck, U. K. Mishra, and S. P. Denbaars,J. Electron. Mater. 24, 1707 (1995).

9. M. D. Craven, P. Waltereit, F. Wu, J. S. Speck, and S. P. DenBaars,Jpn. J. Appl. Phys., Part 2 42, L235 (2003).

10. G. Bauer and W. Richter, Optical characterization of epitaxialsemiconductor layers (Springer Verlag, Berlin, New York, 1996).

11. I. H. Tan, G. L. Snider, L. D. Chang, and E. L. Hu, J. Appl. Phys.68, 4071 (1990).

12. P. Bigenwald, P. Lefebvre, T. Bretagnon, and B. Gil, Phys. Stat.Sol. B 216, 371 (1999).

13. N. Grandjean, B. Damilano, S. Dalmasso, M. Leroux, M. Laugt, and J.Massies, J. Appl. Phys. 86, 3714 (1999).

14. N. Grandjean, J. Massies, and M. Leroux, Appl. Phys. Lett. 74, 2361(1999).

15. I. Jin Seo, H. Kollmer, J. Off, A. Sohmer, F. Scholz, and A.Hangleiter, Phys. Rev. B 57, R9435 (1998).

16. R. Langer, J. Simon, V. Ortiz, N. T. Pelekanos, A. Barski, R. Andre,and M. Godlewski, Appl. Phys. Lett. 74, 3827 (1999).

17. G. Traetta, A. Passaseo, M. Longo, D. Cannoletta, R. Cingolani, M.Lomascolo, A. Bonfiglio, A. Di Carlo, F. Della Sala, P. Lugli, A.Botchkarev, and H. Morkoc, Physica E 7, 929 (2000).

18.M. Leroux, N. Grandjean, M. Laugt, J. Massies, B. Gil, P. Lefebvre,and P. Bigenwald, Phys. Rev. B 58, R13371 (1998).

19. A. Kinoshita, H. Hirayama, P. Riblet, M. Ainoya, A. Hirata, and Y.Aoyagi, MRS Internet J. Nitride Semicond. Res. 5, W11.32 (2000).

CONCLUSION

This concludes the description of the preferred embodiment of thepresent invention. The following describes some alternative embodimentsfor accomplishing the present invention.

For example, variations in non-polar (Al,In,Ga)N quantum wells andheterostructures design and MOCVD growth conditions may be used inalternative embodiments. Moreover, the specific thickness andcomposition of the layers, in addition to the number of quantum wellsgrown, are variables inherent to quantum well structure design and maybe used in alternative embodiments of the present invention.

Further, the specific MOCVD growth conditions determine the dimensionsand compositions of the quantum well structure layers. In this regard,MOCVD growth conditions are reactor dependent and may vary betweenspecific reactor designs. Many variations of this process are possiblewith the variety of reactor designs currently being using in industryand academia.

Variations in conditions such as growth temperature, growth pressure,VIII ratio, precursor flows, and source materials are possible withoutdeparting from the scope of the present invention. Control of interfacequality is another important aspect of the process and is directlyrelated to the flow switching capabilities of particular reactordesigns. Continued optimization of the growth conditions will result inmore accurate compositional and thickness control of the integratedquantum well layers described above.

In addition, a number of different growth methods other than MOCVD couldbe used in the present invention. For example, the growth method couldalso be molecular beam epitaxy (MBE), liquid phase epitaxy (LPE),hydride vapor phase epitaxy (HVPE), sublimation, or plasma-enhancedchemical vapor deposition (PECVD).

Finally, substrates other than sapphire could be employed. Thesesubstrates include silicon carbide, gallium nitride, silicon, zincoxide, boron nitride, lithium aluminate, lithium niobate, germanium,aluminum nitride, and lithium gallate.

The foregoing description of one or more embodiments of the inventionhas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise form disclosed. Many modifications and variations are possiblein light of the above teaching. It is intended that the scope of theinvention be limited not by this detailed description, but rather by theclaims appended hereto.

What is claimed is:
 1. A semiconductor device structure, comprising: (a)an initial non-polar (Al,B,In,Ga)N layer in the structure, wherein theinitial non-polar (Al,B,In,Ga)N layer has a growth surface forsubsequent layers that is a grown surface, and the grown surface is anon-polar plane; and (b) one or more subsequent non-polar (Al,B,In,Ga)Nlayers grown directly on or above the growth surface of the initialnon-polar (Al,B,In,Ga)N layer; (c) wherein the non-polar (Al,B,In,Ga)Nlayers form at least one non-polar (Al,B,In,Ga)N quantum well and thenon-polar (Al,B,In,Ga)N quantum well has a width greater than 50 Å forgenerating light at a peak photoluminescence (PL) intensity.
 2. Thedevice of claim 1, wherein the initial non-polar (Al,B,In,Ga)N layer isgrown on or above a substrate.
 3. The device of claim 2, wherein theinitial non-polar (Al,B,In,Ga)N layer is grown on or above a nucleationlayer grown on the substrate.
 4. The device of claim 3, wherein thesubstrate is an r-plane sapphire.
 5. The device of claim 1, wherein thenon-polar (Al,B,In,Ga)N quantum well has a barrier layer doped withsilicon.
 6. The device of claim 5, wherein the silicon has aconcentration of 2×10¹⁸ cm⁻³.
 7. The device of claim 1, wherein thenon-polar (Al,B,In,Ga)N quantum well has a width between 50 Å and 55 Åfor generating light at a peak photoluminescence (PL) intensity.
 8. Thedevice of claim 7, wherein the non-polar (Al,B,In,Ga)N quantum well hasa width of 52 Å for generating light at a peak photoluminescence (PL)intensity.
 9. The device of claim 1, wherein the non-polar (Al,B,In,Ga)Nquantum well is a non-polar GaN/AlGaN quantum well.
 10. A method forfabricating a semiconductor device structure, comprising: (a) growing aninitial non-polar (Al,B,In,Ga)N layer in the structure, wherein theinitial non-polar (Al,B,In,Ga)N layer has a growth surface forsubsequent layers that is a grown surface, and the grown surface is anon-polar plane; and (b) growing one or more subsequent non-polar(Al,B,In,Ga)N layers directly on or above the growth surface of theinitial non-polar (Al,B,In,Ga)N layer; (c) wherein the non-polar(Al,B,In,Ga)N layers form at least one non-polar (Al,B,In,Ga)N quantumwell and the non-polar (Al,B,In,Ga)N quantum well has a width greaterthan 50 Å for generating light at a peak photoluminescence (PL)intensity.
 11. The method of claim 10, wherein the initial non-polar(Al,B,In,Ga)N layer is grown on or above a substrate.
 12. The method ofclaim 11, wherein the initial non-polar (Al,B,In,Ga)N layer is grown onor above a nucleation layer grown on the substrate.
 13. The method ofclaim 12, wherein the substrate is an r-plane sapphire.
 14. The methodof claim 10, wherein the non-polar (Al,B,In,Ga)N quantum well has abarrier layer doped with silicon.
 15. The method of claim 14, whereinthe silicon has a concentration of 2×10¹⁸ cm⁻³.
 16. The method of claim10, wherein the non-polar (Al,B,In,Ga)N quantum well has a width between50 Å and 55 Å for generating light at a peak photoluminescence (PL)intensity.
 17. The method of claim 16, wherein the non-polar(Al,B,In,Ga)N quantum well has a width of 52 Å for generating light at apeak photoluminescence (PL) intensity.
 18. The method of claim 10,wherein the non-polar (Al,B,In,Ga)N quantum well is a non-polarGaN/AlGaN quantum well.